Color positive photographic prints intended for direct viewing are typically made by imagewise exposing a support coated with layers sensitive to each of the blue, green and red regions of the visible spectrum and which yield yellow, magenta and cyan dye images, respectively. Exposure is commonly to a color negative film which contains a negative image of the original scene. If the exposure latitude of the color print material is less than the full range of densities recorded in the film, reproduction of detail in the print will be poor.
Exposure latitude is a measure of the ability of a recording material to represent differences in intensity of exposure by differences in density. Thus, materials with a wide exposure latitude would respond to a wide range of exposure intensities by showing differences in image density, while materials with a narrow exposure latitude would, for the same range of exposure intensities, show fewer differences in density. Heretofore, exposure latitude typically has been modified by manipulation of the silver halide emulsion. For example, increasing the range of grain sizes in an emulsion is known to extend the exposure latitude, while narrowing the range of grain sizes is known to decrease exposure latitude. U.S. Pat. No. 3,663,228, issued May 16, 1972, to C. W. Wyckoff, discloses other techniques for extending the exposure latitude of color photographic materials.
In my copending U.S. Pat. Application Ser. No. 87,276, filed Aug. 20, 1987, now U.S. Pat. No. 4,902,609 issued Feb. 20, 1990 I describe a novel technique for extending exposure latitude of photographic materials. In accordance with that invention, there is provided a color photographic element comprising a support and first and second silver halide emulsion layers. The first emulsion layer is sensitized to a first region of the spectrum and the second emulsion layer is sensitized to a second region of the spectrum and, to a limited degree, to the first region of the spectrum. Dye density formed in the second emulsion layer as a result of its exposure to the first region of the spectrum, adds to the dye density formed in the first emulsion layer and thereby extends the exposure latitude. This is perceived as an increase in the degree of detail viewable in the image.
While this is a useful technique, it requires adjusting the degree of spectral sensitivity of the emulsion in the second emulsion layer for two different regions of the spectrum. It would be desirable to provide a means for accomplishing a similar extension of exposure latitude without having to manage the spectral sensitivity of an emulsion to two different regions of the spectrum.
I have found that exposure latitude can be extended by providing a color photographic material comprising;
a support
first and second silver halide emulsion layers each sensitive to a different region of the electromagnetic spectrum and each layer containing a coupler that forms a dye complementary in color to the principal spectral sensitivity of the emulsion, and
a non-light sensitive interlayer between the two emulsion layers,
wherein:
the interlayer contains a coupler that forms, as a function of development of the first emulsion layer, a dye complementary in color to the principal sensitivity of the second emulsion layer.